# A proton with velocity v completes a circle with radius r in uniform magnetic field.what should be the velocity of alpha particle so that it completes a circle with same radius under the influence of the same magnetic field?

##### 1 Answer

The force experienced by a particle of charge

#(mv^2)/r=qvB_m#

#=>v=(qrB_m)/m#

Where

In our problem both proton and

For proton the above relation becomes

#=>v=(q_prB_m)/m_p#

And for

#=>v_alpha=(q_alpharB_m)/m_alpha#

So

Hence